Ultrasonic surgical aspiration needle assembly with molded hub

ABSTRACT

A surgical needle assembly for attachment to an ultrasonic handpiece includes an elongated metal cannula having a distal end and a proximal end. A hub is insert molded onto the cannula generally towards the cannula proximal end and formed from a material having an ultimate strength at least twice a peak cyclical stress force at a joint between the elongated metal cannula and the hub when the surgical needle assembly is in use with the ultrasonic handpiece. The hub material has a stiffness sufficient to limit a motion of the elongated metal cannula to less than 1.5 times an expected peak to peak stroke length when the surgical needle assembly is in use with the ultrasonic handpiece. The hub includes structure for mating attachment to the ultrasonic handpiece.

FIELD

The present disclosure relates to ultrasonic surgical aspiration needleassemblies. More particularly, the present disclosure relates toultrasonic needle assemblies having a metal needle or cannula molded toa hub that is for attachment to an ophthalmic surgical handpiece.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

The hub and shaft portions of ultrasonic phacoemulsification (phaco)needle assemblies used in, for example cataract surgery, typically aremachined monolithically out of a rigid metal, most commonly titanium.Soft compliant tips have been proposed for the distal end of phacocannula shafts, but the use of non-metal materials for the hubs has notbeen proposed. The metal hub and metal cannula shaft are rigid andstrong enough to withstand the forces exerted by ultrasonic vibrationand to efficiently transmit the ultrasonic vibrations from a vibrationsource through the hub and cannula for emulsifying tissue at the distalend of the needle assembly.

Molding materials, such as polymers, are more compliant than metal andare less efficient in transferring ultrasonic energy compared to metal.Multi-part irrigation (non-vibrating) needle assemblies have beenproposed that included a compliant o-ring between a substantiallystraight shaft and a larger hub, but these are not intended to transmitultrasonic energy. In addition, it is also known for injection needleassemblies to have a hub molded on a metal needle; again these needleassemblies are not intended to transmit ultrasonic energy and there isno indication that such needle assemblies would withstand ultrasonicvibration.

Machining a hub and needle assembly is expensive and becomesincreasingly expensive and difficult as the cannula outer diameterbecomes smaller, as the cannula length becomes longer, and as thecannula wall thickness becomes thinner. The difficulty of machining ahub and needle assembly was experienced when attempting to build needleassemblies for posterior ultrasonic vitreous removal described inco-pending U.S. patent application Ser. No. 14/020,386 entitledVibrating Surgical Device for Removal of Vitreous and Other Tissue. Theultrasonic needle assembly for vitreous removal is longer than a typicalphaco needle assembly to enable the needle assembly to span across theposterior segment of the eye. The ultrasonic vitreous cannula also has asmaller outer diameter (OD) compared to a typical phaco cannula to allowthe vitreous needle assembly to pass through entry alignment cannulasused in sutureless posterior surgery. It is also desirable for theultrasonic vitreous cannula to have an inner diameter (ID) as large aspossible to remove vitreous as efficiently as possible. Since the OD ofthe vitreous cannula is limited by the entry alignment cannula, tomaximize the vitreous cannula ID, it is desirable to minimize the wallthickness of the vitreous cannula.

Further, it is desirable to create an ultrasonic surgical needleassembly that is of low enough cost to be a single-use, disposableneedle assembly. Producing an ultrasonic surgical needle assembly at acost to justify a single-use needle assembly and that can accommodateespecially small gauge needle assemblies of longer than standard lengthwith thinner than normal needle assembly wall thickness would bedesirable.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an elevation of an example surgical needle assembly;

FIG. 2 is a cut away elevation of FIG. 1 along line 2-2;

FIG. 3 is a partial perspective of FIG. 1;

FIG. 4 is a partial perspective and partial cut away of an alternateexample;

FIG. 5 is a partial perspective and partial cut away of anotheralternate example;

FIG. 6 is a partial perspective and partial cut away of an examplesurgical needle assembly attached to an ultrasonic handpiece;

FIG. 7 is a partial perspective and partial cut away of another examplesurgical needle assembly attached to an ultrasonic handpiece; and

FIG. 8 is a partial view of a portion of FIG. 7.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

A surgical needle assembly 10 for attachment to an ultrasonic handpieceis shown in FIG. 1. The needle assembly 10 includes an elongated metalcannula 12 having a distal end 14 and a proximal end 16. A hub 18 isinsert molded onto the cannula 12 generally towards the cannula proximalend 16 and is formed from a material having an ultimate strength atleast twice a peak cyclical stress force at a joint 20 between theelongated metal cannula 12 and the hub 18 when the surgical needleassembly is in use with the ultrasonic handpiece (not shown). The hubmaterial also has a stiffness sufficient to limit a motion of theelongated metal cannula 12 relative to portions of hub 18 to less than1.5 times an expected peak to peak stroke length when the surgicalneedle assembly 10 is in use with the ultrasonic handpiece. The hub 18also includes structure 22 for mating attachment to the ultrasonichandpiece (not shown). It is believed that hub mating structure 22 willperform best as a male structure, such as the threads shown. However,hub mating structure may also be formed as a female structure. Dependingon the ultrasonic levels used, a female hub mating structure may requirethe use of an over-sleeve to prevent the hub from expanding and slippingas the hub material heats up during use to maintain fluid tightconnection with the ultrasonic handpiece. Other mating structure besidesthreads may also be used.

Hub 18 may insert molded onto cannula 12 by any acceptable moldingtechnique and may be formed from a polymer, such as polyetherimide (PEI)which is sold under the brand name Ultem™ by a variety of companies.Ultem™ HU1010 and HU1010K currently manufactured by SABIC have beenfound to be effective hub materials. Other materials, depending on theapplication may also be acceptable such as polyetheretherketone (PEEK),polyaryletherketone (PAEK), polysulfone (PSU), polyethersulfone (PESU),polyphenylsulfone (PPSU), self-reinforced polyphenylene (SRP),polycarbonate (PC), or other suitable materials. Materials may also usefillers, such as glass, as long as they are certifiable asbiocompatible. The term “insert molded” as used in this disclosurerefers to the process of molding or forming plastic or other polymersaround other, non-plastic, non-polymer parts (inserts). Joint 20 is bestseen in FIG. 2 as the thick black line.

Cannula 12 may be formed from an appropriate biocompatible metal such asstainless steel, titanium, or nickel-titanium alloy (aka, Nitinol).

The properties of the hub polymer may be selected to improve variousaspects of surgical performance. For instance, an ultimate strength ofthe hub material may be selected to prevent joint failure under theanticipated cyclical stresses to which the horn-hub-cannula interfacewill be subjected under normally anticipated operating conditions.Alternatively or additionally, a melting point of the hub polymer may beselected to be low enough to melt or deform if subjected to autoclavetemperatures to prevent reuse of single use needle assemblies.

Proximal end 16 may have attachment structure formed on cannula 12 forenhancing an adhesion or grip of the hub material to cannula 12, and/orto improve the shear stiffness of the hub material. For instance,chemical etching or deposition techniques may be used to roughen theouter surface of cannula 12 (not shown). Grooves 24 (cross-hatchedlines) and elevated lands 26 (diamond-shapes) of FIG. 4 may be created,e.g. using laser etching to improve the grip between cannula 12 and hub18. Care should be taken, especially with small gauge cannulas, e.g. 23or 25 ga., having thin walls, when etching grooves 24 because it hasbeen found that the grooves create a stress failure location duringultrasonic operation. Deposing material onto cannula 12 (not shown) mayprovide a more robust solution if enhanced adhesion between cannula 12and hub 18 is required for a particular design. Alternatively, ringsheaths 28, as shown in FIG. 5, may be attached to cannula 12 to reducethe thickness of the hub portion subjected to shear forces during use;thus enhancing the stiffness of the joint 20, and to provide axialsurfaces 30 for transmitting axial push and pull forces directly tocannula 12. The ring sheaths 28 may be attached to cannula 12 by anyacceptable manner, such as adhesives, welding, laser welding, crimping,etc.

The male structure 22 may include threads formed in the hub 18, as shownin FIGS. 1-3 or may include a press-fit bearing surface 22′, as shown inFIGS. 4-6 for creating an interference attachment with a horn of thehandpiece. As shown in FIG. 6, the male structure may also have a shortsection, shown generally at 30, with a smaller OD to facilitateinsertion into the horn 32 during press-installation. As shown, the malestructure may also have a tapered section to further facilitate theinitial press installation.

If the hub 18 is threaded, the handpiece 34, shown in FIG. 7, may have athreaded section, shown generally at 36, for mating with the hub 18. Thethreads of handpiece 34 and hub 18 may have any acceptable type ofthreads to facilitate a liquid-tight seal during use. For example, thethreads may have a tapered section similar to known pipe threads.

Alternatively, when the surgical needle assembly 10 is attached to theultrasonic handpiece 34 via threads, a thread fill material 38, as shownin FIG. 8, may be added for enhancing the attachment of the surgicalneedle assembly 10 to the ultrasonic handpiece 34 and enhancing aliquid-tight seal with the ultrasonic handpiece 34. The thread fillmaterial may be any acceptable material that enhances the attachment ofhub 18 to the ultrasonic handpiece 34, e.g. Loctite® M121HP or M11fl.The hub 18 may also include a flange portion 40 that is sufficientlythick for producing a liquid-tight seal with the ultrasonic handpiece34. The flange portion 40 must be sufficiently thick to providestructural stability and not deform so that a tight seal at 42 may beformed between the flange portion 40 and the handpiece 34.

FIG. 3 provides a good perspective view of hub 18, including the wrenchflats 44 for mating with a wrench to tighten the hub 18 onto ahandpiece.

Producing a commercially effective ultrasonic surgical needle assemblywith an insert molded hub requires that the hub meet at least twoconditions. First, the hub must be strong enough to withstand theexpected forces imposed by the ultrasonic vibrations under normal use.Second, the hub must be stiff enough to sufficiently limit the motion ofthe needle assembly under normal ultrasonic cyclical vibrations. Theseconditions are not expected for needle assemblies used for injections.

Details of the hub design (length, material thickness, material shearmodulus and shear strength, and inclusion of interfering features suchas threads, ridges, cross-holes, etc.) may affect both the stiffness andthe strength of the hub.

To optimize strength, designers may specify longer hubs, which increasethe hub strength by spreading the force out over a larger area to reducestress, or select higher strength materials. Material strength isgenerally specified as threshold stress levels (e.g. units of pressuresuch as MPa (megapascals) or PSI (pounds per square inch)) at whichspecific undesirable effects (e.g. plastic deformation, permanentdeformation, outright failure, etc.) occur in material test samples.

To optimize stiffness, designers may specify longer hubs or thinnermolded hub walls, or selecting stiffer materials. Material stiffness isgenerally specified using one or more modulus values, which specify thematerial stress level required to create a known elastic deformation inthe material. Higher modulus materials typically result in stiffer hubs.

As used in this disclosure, the term ultimate strength (aka tensilestrength), σ_(ts), is the maximum engineering stress (applied loaddivided by the original cross-sectional area of the specimen) in auniaxial stress-strain test. For non-deformable materials, the maximumengineering stress is the nominal stress at which a round bar of thematerial, loaded in tension, separates. For deformable materials, themaximum engineering stress occurs at the onset of necking at strainspreceding breakage (separation). For brittle solids—ceramics, glasses,and brittle polymers—the maximum engineering stress is the same as thefailure strength in tension. For metals and most composites, it islarger than the yield strength, σ_(y), by a factor of between 1.1 and 5because of work hardening or, in the case of composites, load transferto the reinforcement.

As used in this disclosure, the term endurance strength (aka fatiguestrength), S_(Nf), is the value of stress at which failure occurs afterN_(f) cycles. Various multipliers can be applied to account for thedegradation of the hub material and/or joint over the expected use lifeof the needle assembly. Use of a needle assembly continuously for 5minutes, in the cases above, results in stressing it through slightlyless than 10 million cycles. Wohler curves (S-N curves) describing theeffects of cyclical fatigue on the strength of a material subjected tocyclical stress for materials show how much the material strength maydegrade over a given number of cycles. Thus, the designer would selectthe hub component design parameters to ensure that a hub will have anendurance strength after the expected number of stress cycles equal toor greater than the peak cyclical stress force experienced at the jointbetween the cannula and the hub.

Under normal ophthalmic ultrasonic surgical use, hub 18 is acceleratingthe mass of cannula 12 through the harmonic amplitude (stroke length)required for clinical effectiveness. Although cannula 12 and hub 18 arepart of a larger resonant structure with a more complex accelerationprofile, the maximum acceleration of the needle assembly 10 may beconveniently bounded by assuming most motion comes from the horn of theultrasonic handpiece, and cannula 12 is a stiff mass. In this case, anupper bound for the maximum force hub 18 will experience can becalculated asMax Expected Force=X ₀*needle assembly mass*(Harmonic frequency)² =X ₀mω ²

In one example case (Case A) of a cannula 12 having a 41 mm length,0.025″ OD, 0.017″ ID, and a 0.004″ wall made from stainless steel ofdensity 8 g/cm³, driven at 28.5 kHz (approximately 179,000 rad/sec),with a peak-to-peak stroke amplitude (length) of 40 μm (X₀=20 μm), thecannula mass is ˜0.056 grams and the peak force is approximately 36Newtons (about 8 lbs. force).

In a more extreme example case (Case B) of a cannula 12 having a 41 mmlength, 0.025″ OD, 0.013″ ID, and a 0.006″ wall made from stainlesssteel of density 8 g/cm3, driven at 28.5 kHz (approximately 179,000rad/sec), with a peak-to-peak stroke amplitude of 60 μm (X₀=20 μm), thecannula mass is ˜0.077 grams and the peak force is approximately 74Newtons (about 17 lbs. force).

In practice, the thin cannula material may be much more rigid than theover molded hub, but not be perfectly rigid compared to the driving hornof the handpiece. Therefore, the amplitude of motion at hub 18 may besomewhat less than that of distal end 14, resulting in some resonantgain within cannula 12 and a corresponding reduction in the peak forceat hub 18 for a given distal end 14 motion. On the other hand, becauseof possible cyclical fatigue, some additional margin in the needleassembly design may be useful, and needle assembly designs incapable ofwithstanding the peak force calculated above are likely to fail whensubjected to normal expected operational stresses.

Joint strength between cannula 12 and hub 18 can be convenientlyevaluated by pulling on the joint—either by hanging a weight from thecannula or the hub or by use of automated tensile strength tester, suchas those provided by the company Instron®. Although the stress hub 18under goes anchoring cannula 12 to the vibrating horn is shear stress,the overall effective forces in the needle assembly/horn system areaxial or longitudinal. A simple test to ensure the needle assemblydesign is strong enough is to pull on the horn and needle assemblyaxially, close to the joint, and confirm that the joint failure point isabove the peak forces identified above, in Cases A and B. This can bedone on new hubs using a force multiplier (e.g. twice the expected peakcyclical stress force at joint 20) to account for cyclical degradation,or it can be done after driving the needle assembly through anappropriate number of cycles.

Pulling on a batch of Ultem® hubs with a 4-40 UNC (Unified NationalCoarse) thread insert molded onto a 23 gage needle assembly with anInstron® tester resulted in failure points between 25 and 50 lbs., wellin excess of the required forces identified above. It has beendiscovered that the integrity of the molding process affected the jointstrength. Hubs with lower failure points had visible internal defects,such as bubbles, while hubs with higher failure points did not havethese defects.

Designers may, of course, target a higher joint strength to provideadditional design margin to minimize large quantity component failurerates or the potential impact of manufacturing process changes, or toaccount for larger strokes or longer uses.

Stiffness of hub 18 will now be discussed. The hub can be considered asa spring, subject to Hooke's Law (Force=K*displacement). In this view,Force/K=displacement. The hub must be stiff enough that the displacementis not significant under the expected drive forces compared to theoverall desired motion amplitude (stroke length). Using the relationshipalready identified (Force=X₀mω²) and requiring that the displacementacross the hub under this force must be a small factor (1/N) of thedesired amplitude (that is, displacement<X₀/N), it may be understoodthat the effective stiffness K of the hub isForce/displacement={X₀mω²/(X₀/N)} or Nmω².

The theoretical stiffness of a N ideal radially symmetric hub with anOD, ID, length L and material shear modulus of G can be shown to beK=2πG*L*ID/ln(OD/ID). As an example, for molded Ultem hubs withOD=0.112″ (major diameter of the 4-40 thread), ID of 0.025″ (minimum IDof 23 gage needle assemblies), length of 0.3″ and shear modulus G of˜170 kPSI, an estimated stiffness K=5300 lbs./inch or 5.3 lbs./0.001″.Axial pull testing seven samples, on an Instron® tester, suggested thatthe joint had a stiffness of around 4000 lbs./inch, (4 lbs./0.001″ orabout 0.7 Newtons/μm), consistent with the predicted ideal value.

With this design, the flex of hub 18 in Case A for the 36 Newtons (Nt)restoring force is around 50 μm, or more than the peak-to-peak strokelength of 40 μm but less than 1.5 times the peak-to-peak stroke length.Laboratory experience indicates that this level of compliance can betolerated.

It can be appreciated that the spring action at the joint 20, combinedwith the mass of the cannula, forms a mass-spring system with a resonantfrequency for the needle assembly. For such a lumped model, the harmonicresonant frequency ω₀ is known to be ω₀=√(k/m). For the example givenabove, k˜930000 Nt/m, m˜0.000056 kg, ω₀˜128,000 radians/sec, and theresonant frequency is ˜20 kHz. The stiffer the joint, the higher theresonant frequency of the needle assembly. As noted above, resonantfrequencies of the needle assembly that are at least half the planneddrive frequency can be tolerated, but needle assembly resonantfrequencies equal to or greater than the planned drive frequency arepreferred.

As with hub strength, hub stiffness is more important for ultrasonicallydriven needle assemblies than for injection needle assemblies. If aninjection needle assembly shifts slightly forward during an injection,the deflection does not affect the quality of the injection, and manyinjection needle assemblies are mounted onto sterile plastic syringes,which are, themselves, quite compliant. However, unwanted or excessivedeflection for an ultrasonic needle assembly may be ineffective orpossibly dangerous. Hub design stiffness can be conveniently evaluatedat the same time as hub design strength, by observing the needleassembly displacement as the axial force increases on an automatedtensile strength tester, as referenced above, at forces below thefailure force. The slope of the resulting stress/displacement curverepresents the hub design stiffness. However, it should be noted thatthe measurement system should be significantly stiffer than the expectedjoint stiffness for reliable data. If the measurement system is notsufficiently stiff, the measured compliance will be somewhat less thanthe actual compliance.

An additional benefit of designing the hub to be stiff is a reduction inhub heating compared to a more compliant hub. The compliant hub can betreated as a spring. The energy stored in the spring at maximumextension is a function of the force being applied and the springconstant. In practice, a portion of that energy is absorbed anddissipated by the spring each cycle creating heat and causing the springto gradually heat up. Designing hubs that are relatively stiff (so theydo not store as much energy in each force cycle) and selecting materialsthat have low mechanical dissipation loss factors (so that they do notabsorb the energy as they stretch) and thermally stable mechanicalproperties (so that the performance does not change if the hub materialheats up due to cyclical actuation) will result in improved performanceof the needle assembly.

An alternate example description of a surgical needle assembly forattachment to an ultrasonic handpiece may be an elongated metal cannulahaving a distal end and a proximal end, as described above. A hub, asdescribed above, is insert molded onto the cannula generally towards thecannula proximal end and formed from a material having an endurancestrength equal to or greater than a peak cyclical stress force at ajoint between the elongated metal cannula and the hub when the surgicalneedle assembly is in use with the ultrasonic handpiece. The hubmaterial may also have a stiffness sufficient to limit a motion of theelongated metal cannula to less than 1.5 times an expected peak to peakstroke length when the surgical needle assembly is in use with theultrasonic handpiece. The hub may also include a male structure formating attachment to a female structure of the ultrasonic handpiece. Thealternate example may have the same features and be formed of the samematerials as described above.

Another alternate example description of a surgical needle assembly forattachment to an ultrasonic handpiece may be an elongated metal cannulahaving a distal end and a proximal end. A hub is insert molded onto thecannula generally towards the cannula proximal end and formed from amaterial having an endurance strength equal to or greater than a peakcyclical stress force at a joint between the elongated metal cannula andthe hub when the surgical needle assembly is in use with the ultrasonichandpiece. The surgical needle assembly has a resonant frequency that isat least half of a nominal operating frequency of the ultrasonichandpiece. The hub includes a male structure for mating attachment to afemale structure of the ultrasonic handpiece. Again, this alternateexample may have the same features and be formed of the same materialsas described above.

Still another alternate example may be described with respect to anultrasonic surgical handpiece having a body. An ultrasonic vibrationassembly is held within the body. A surgical needle assembly is attachedto a distal portion of the ultrasonic vibration assembly. The surgicalneedle assembly includes an elongated metal cannula having a distal endand a proximal end. A hub is insert molded onto the cannula generallytowards the cannula proximal end and formed from a material having anendurance strength equal to or greater than a peak cyclical stress forceat a joint between the elongated metal cannula and the hub when thesurgical needle assembly is in use with the ultrasonic handpiece. Thesurgical needle assembly has a resonant frequency that is at least halfof a nominal operating frequency of the ultrasonic handpiece. The hubincludes a male structure for mating attachment to a female structure ofthe ultrasonic handpiece. Again, the surgical needle assembly of thisalternate example may have the same features and be formed of the samematerials as described above. The ultrasonic vibration assembly may bepiezoelectric or magneto-resistive assemblies that are well-known, suchas shown in FIG. 7 at 35.

Yet another alternate example may be described with respect to anultrasonic surgical handpiece having a body. An ultrasonic vibrationassembly held within the body. An elongated metal cannula is insertmolded onto a distal portion of the ultrasonic vibration assembly. Inthis alternate example, the hub may be formed and insert molded with theultrasonic surgical handpiece and the elongated metal cannulasimultaneously. That is the male structure described above is not formedprior to attachment to the handpiece and then threaded or press-fit ontothe handpiece, rather the male structure is formed on the elongatedmetal cannula and attached to the handpiece by injection molding. Forexample, the hub 18 of FIG. 6 could be attached to cannula 12 and horn32 via injection molding rather than the press-fit example describedabove.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure. Exampleembodiments are provided so that this disclosure will be thorough, andwill fully convey the scope to those who are skilled in the art.Numerous specific details are set forth such as examples of specificcomponents, devices, and methods, to provide a thorough understanding ofembodiments of the present disclosure. It will be apparent to thoseskilled in the art that specific details need not be employed, thatexample embodiments may be embodied in many different forms and thatneither should be construed to limit the scope of the disclosure. Insome example embodiments, well-known processes, well-known devicestructures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. When an element or layer is referred to as being “on,” “engagedto,” “connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

What is claimed is:
 1. An ultrasonic surgical handpiece comprising: abody; an ultrasonic vibration assembly held within the body; and asurgical needle assembly attached to a distal portion of the ultrasonicvibration assembly, the surgical needle assembly including: an elongatedmetal cannula having a distal end and a proximal end; a hub insertmolded onto the cannula generally towards the cannula proximal end andformed from a material having an endurance strength equal to or greaterthan a peak cyclical stress force at a joint between the elongated metalcannula and the hub when the surgical needle assembly is in use with theultrasonic handpiece; wherein the surgical needle assembly has aresonant frequency that is at least half of a nominal operatingfrequency of the ultrasonic handpiece; and wherein the hub includesstructure for mating attachment to the ultrasonic handpiece.
 2. Thesurgical needle assembly of claim 1 wherein the elongated metal cannulafurther includes attachment structure formed on the cannula forenhancing an adhesion of the hub to the cannula.
 3. The surgical needleassembly of claim 1 wherein the elongated metal cannula is formed fromone of stainless steel and titanium.
 4. The surgical needle assembly ofclaim 1 wherein the hub is formed from one of polyetherimide,polyaryletherketone, polysulfone, polyethersulfone, andpolyphenylsulfone.
 5. The surgical needle assembly of claim 1 whereinthe hub includes a flange portion that is sufficiently thick forproducing a liquid-tight seal with the ultrasonic handpiece.
 6. Thesurgical needle assembly of claim 1 wherein the hub mating structureincludes male threads formed in the hub.
 7. The surgical needle assemblyof claim 6 wherein the surgical needle assembly is attached to theultrasonic handpiece via the threads and further includes a thread fillmaterial for enhancing the attachment of the surgical needle assembly tothe ultrasonic handpiece and enhancing a liquid-tight seal with theultrasonic handpiece.